3-ethylxanthine has been studied regarding its vasodilatory effects (LeRoy et al.; J. Pharm. Exptl. Ther. 69 (1940) pages 45-51). Furthermore, J. Ruttink (Rec. trav.chim. 57 (1938) 819-823 and Chemische En Pharmakologische Onderzoekingen in de Purinereeks, in het Bijzonder van Aethyl-xanthinen, Diss. Delft, 1938) has studied the effect of 3-ethylxanthine on frog muscle, its diuretic effect and its effect on the heart and the central nervous system.
Theophylline and various salts thereof are used in the treatment of chronic obstructive airway disease (COAD) and cardiac disease. Major therapeutic effects of theophylline are to relax bronchial smooth muscle and stimulate heart muscle. The major drawback with theophylline therapy is that the drug with a significant frequency produces toxic side-effects; most common are nausea and gastric distress, most serious are convulsions, which may lead to death.